1. Field of the Invention
The present invention is related to the production of hydrogen and/or carbon monoxide rich gases by steam reforming of hydrocarbons. In particular, the present invention involves a copper containing nickel reforming catalyst for use in the steam reforming of a hydrocarbon feedstock.
2. Description of the Related Art
In the known processes for the production of hydrogen and/or carbon monoxide rich gases, a mixture of hydrocarbons and steam and/or carbon dioxide is passed at elevated temperature and pressure through a reactor packed with a catalyst, mainly consisting of nickel as the active catalytic component.
Hydrocarbon feedstocks suitable for steam reforming are for instance natural gas, refinery off-gases, propane, naphtha and liquified petroleum gases. Taking methane as an example, the reactions, which take place, can be represented by the following equations: EQU CH.sub.4 +H.sub.2 O.fwdarw.CO+3H.sub.2 ( 1) EQU CH.sub.4 +CO.sub.2 .fwdarw.2CO+2H.sub.2 ( 2) EQU CO+H.sub.2 O.fwdarw.CO.sub.2 +H.sub.2 ( 3)
Raw product gas leaving the steam reforming reactor is conventionally processed by condensation and liquid-gas phase separation treatment subsequent to the steam reforming. The liquid process condensate, mainly consisting of water, is then recycled back to the steam reforming section via a boiler for steam generation.
Prior to introduction into the boiler, the condensate has in many plants to be subjected removal of water soluble compounds and salts. For that purpose, the condensate is passed through a demineralization unit operating typically on ion-exchange resins.
A major problem in the conventional steam reforming process arises during purification of the process condensate, especially condensate from steam reforming of a feedstock with a high content of nitrogen, like natural gas from certain fields.
Nitrogen contained in the feedstock reacts with hydrogen to form ammonia by the reaction: EQU N.sub.2 +3H.sub.2 .fwdarw.2NH.sub.3 ( 4)
when passing through a bed of nickel steam reforming catalyst. Ammonia in the raw product gas is almost quantitatively removed into the process condensate during processing of the gas. Amounts of ammonia of up to 300 parts per million in the process condensate are not unusual, when processing raw product gas from the steam reforming of natural gas.
Such high concentrations of ammonia demand frequent regeneration or renewal of expensive ion-exchange materials used for demineralisation of the process condensate, which is inconvenient to the operation of the steam reforming process.